1. Field of the Invention
This invention relates to a mineral wool insulation product and more particularly to a mineral wool insulation product that is substantially free of crystalline silica.
2. Description of the Prior Art
In U.S. Pat. No. 3,470,062 there is disclosed a ceramic acoustical water-laid sheet in which mineral wool, Mississippi M&D clay and water are admixed to form a homogeneous slurry. A water-laid sheet is formed from the slurry containing between 20 per cent and 65 per cent by weight clay, between 35 per cent and 80 per cent by weight mineral wool and between 45 per cent and 75 per cent by weight water. The water-laid sheet is thereafter dried to remove the water and fired to 1,000.degree. to 1,500.degree.F to form a ceramic bonded board product.
It is known that mineral wool insulation product containing M&D clay comprise superior products from the standpoint of excellent physical characteristics. However, it has been found that the Mississippi M&D clay has about 13.6 per cent by weight free (uncombined) crystalline silica and when a dried product containing M&D clay is shaped or formed by sawing, grinding and the like, the free crystalline silica contained in the M&D clay is released into the atmosphere. Free crystalline silica may have deleterious effects to the health of those present when it is introduced into the atmosphere, constituting a silicosis-inducing work atmosphere.
There is a need for a mineral wool fiber insulation that has the desirable properties of a mineral wool fiber insulation containing M&D clay without the substantial quantities of free crystalline silica present in a product containing M&D clay.